Description

An issue in the ugw-editfile method of /cgi-bin/wwwugw.cgi in MBS-Solutions X-Serie Gateway firmware V6_00_05 allows a remote authenticated user with the low-privileged Standard role to write arbitrary content to files within /uxx/config/ and /ugw/config/.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.3",
  "pubDate": "2026-09-04T16:17:58.813Z",
  "pubdate": "2026-09-04T16:17:58.813Z",
  "executiveSummary": "This vulnerability involves an improper access control flaw within the ugw-editfile method of the /cgi-bin/wwwugw.cgi script in MBS-Solutions X-Serie Gateway firmware version V6_00_05. The flaw permits a remote authenticated user assigned the low-privileged Standard role to perform unauthorized write operations to sensitive configuration directories.\nSpecifically, the vulnerability allows for the modification of arbitrary files located within the /uxx/config/ and /ugw/config/ filesystem paths. Because these directories contain critical system and application configuration data, the ability to inject arbitrary content represents a significant security risk.\nAn attacker can exploit this condition to alter system behavior, modify network settings, or inject persistent malicious configurations that could lead to full device compromise or administrative control. Exploitation requires the attacker to possess valid credentials for a low-privileged account, placing the system at risk from malicious insiders or attackers who have compromised a standard user session. The lack of sufficient server-side validation or path restriction on the ugw-editfile function is the primary factor facilitating this unauthorized file access.\nThe risk implication is high, as the vulnerability circumvents intended privilege boundaries, potentially allowing for lateral movement or persistence within the gateway environment.",
  "technicalDetails": "The root cause of this vulnerability lies in an insecure implementation of the ugw-editfile method within the /cgi-bin/wwwugw.cgi CGI script. The application fails to adequately sanitize or restrict user-supplied input regarding target file paths and fails to enforce robust authorization checks that should prevent a user with a Standard privilege level from modifying critical system configuration files.\nThe affected component, /cgi-bin/wwwugw.cgi, serves as a gateway management interface. When the ugw-editfile method is invoked, the application logic does not perform a secure check to verify if the authenticated user has the necessary administrative permissions to modify files outside of the user's defined scope or in protected directories.\nThe attack flow proceeds as follows: First, the attacker establishes a valid session on the MBS-Solutions X-Serie Gateway using credentials associated with the low-privileged Standard role. Second, the attacker crafts a malicious HTTP request targeting the /cgi-bin/wwwugw.cgi endpoint, specifying the ugw-editfile method. The request includes parameters that point to sensitive files within the /uxx/config/ or /ugw/config/ directories and contains the payload intended for injection.\nBecause the backend process lacks sufficient path traversal prevention and authorization granularity, the application honors the request and proceeds to overwrite the targeted files with the attacker's provided content. This process bypasses the intended security policy where only higher-privileged administrators should be allowed to modify system-level configurations.\nThe technical impact of successful exploitation is profound. By overwriting configuration files, an attacker can modify parameters related to network traffic routing, service execution, or security policies. Furthermore, if the configuration files include scripts or directives that are parsed by the system upon initialization or service restart, the attacker could achieve arbitrary code execution or persistence by injecting shell commands or malicious configurations into the system startup sequence.\nThe vulnerability is specific to firmware version V6_00_05. The exposure is remote, as the management interface is typically accessible over the network. Given that no strict validation exists on the input parameters during the file write operation, the service remains vulnerable to any user capable of authenticating to the device."
}